• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.1-9
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• 2009

When a rock slope is excavated adjacent to a existing tunnel, the behavior of the existing tunnel in the jointed rock masses is greatly influenced by the joint conditions and slope status. In this study, the effects of joint dip and slope angle close to a tunnel are investigated through a large scale model using a biaxial test equipment ($3.1\;m\;{\times}\;3.1\;m\;{\times}\;0.50\;m$ (width $\times$ height $\times$ length)). The jointed rock masses were built by concrete blocks. The diameter of the modeled tunnel is 0.6 m and the dip angles of joint vary in the range of $0-90^{\circ}$. In addition, the excavated slope angle varies within $30{\sim}90^{\circ}$. Deformational behaviors of the tunnel were analyzed in consideration of joint dip and slope angle. With increase of the joint dip and slope angle, the magnitude of tunnel distortion and the moment of tunnel lining were increased. Rock mass displacement in horizontal was also dependent on the joint dip and the excavated slope angle, which indicated the optimal slope reinforcement for a specific rock mass conditions.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.292-304
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• 2019

Limestone joint surfaces with smooth roughness were experimented by means of both the individual direct shear tests based on the KSRM standard test method and the multi-stage direct shear test to apply the stepwise vertical stresses. Changes in the roughness of the joint surfaces before and after the shear tests were examined and the difference between the two kinds of tests mentioned above was analyzed. In both tests, the shear resistance increased as the joint roughness increased and the maximum shear stress required for shearing the joint surface increased as the vertical stress increased. The peak friction angle obtained by the multi-stage direct shear tests was only 63% of that obtained by the individual direct shear tests. In the multi-stage direct shear test, the initial engagement of the concave-convex parts changes frequently during stepwise shearing process, which deforms the original roughness of a joint surface. Accordingly, the individual direct shear test is thought to be more effective when obtaining the friction angle of the rock joint surfaces. Limestone joint surfaces with smooth roughness of JRC value 4~8 were found to have peak friction angle of $47^{\circ}$, residual friction angle of $38^{\circ}$ and cohesion of 37 kPa.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.642-649
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• 2023

The purpose of this study was to analyze the effects of knee joint injury experiences of judo players on kinematic factors and center of pressure factors during uchimata. Among right-handed male college judo players specializing in uchimata, 13 people who had a knee joint injury experience(age, 20.69.1±0.75 years; height, 172.85±4.81 cm; body mass, 74.92±5.51 kg; and career, 8.92±0.95 years) and 13 people who did not have a knee joint injury experience(age, 21.08.1±0.76 years; height, 172.54±6.32 cm; body mass, 76.62±9.09 kg; and career, 9.46±0.94 years) within the last 2 years were divided into two groups and participated as subjects. The two groups were evaluated for differences in ankle, knee, and hip joint angle variables, COP range, and velocity components during uchimata. As a result of the study, the EIG group showed smaller values in the knee joint flexion angle at E3 and the hip joint extension angle at E4 during uchimata than the NIG group. In addition, the EIG group showed lower values in the range of motion of the COP and forward movement velocity of the COP in the one-leg support phase than the NIG group.

• Physical Therapy Korea
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• v.22 no.2
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• pp.21-29
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• 2015

This study investigated the effect of a load of 15% body weight on trunk, pelvis and hip joint coordination and angle variability in subjects with and without chronic low back pain (CLBP) during an anterior load carriage task. Thirty volunteers participated in the study (15 without CLBP, 15 with CLBP). All participants were asked to perform an anterior carriage task with a load of 15% body weight. The outcome measures included the means and standard deviations for measurements of three-dimensional coordination and angle variability of the trunk, pelvis and hip joint. As CLBP patient group .06, control group .70, the correlation coefficient between the groups showed a significant difference only in trunk-pelvic in the sagittal plane (p<.05). Angle variability of CLBP patient group increased significantly in the trunk in frontal plane, the pelvis in all sagittal plane, frontal plane, transverse plane, and the hip in sagittal plane, the hip in frontal plane than angle variability of control group (p<.05). This results mean that the CLBP patient group showed a disconnected coordination pattern in the trunk-pelvis in the sagittal plane, an increased pelvic angle variability in all three planes, and hip angle variability in the sagittal, and frontal planes. The CLBP patient group may have developed a compensatory movement of the pelvis and hip joint arising from the changed stability due to the abnormal coordination patterns of the trunk-pelvic in the sagittal plane. Therefore, CLBP symptoms can potentially worsen in the pelvis and adjacent hip joint in CLBP patients who perform weight-related behaviors in their daily lives. Further research is needed to determine the three-dimensional characteristics of the electromyography and neuromuscular aspects of subjects with CLBP.

• Journal of Korean Foot and Ankle Society
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• v.10 no.2
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• pp.196-200
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• 2006

Purpose: To study prognostic factors of unilateral calcaneus fracture underwent surgery. Materials and Methods: We selected appropriate 60 cases of 236 calcaneus fracture cases between March 1985 and March 2004, and analyzed the correlation between sex, age, smoking, injury mechanism, Essex-Lopresti classification of calcaneus fracture, preoperative Bohler angle, postoperative Bohler angle, postoperative 1 year Bohler angle and Visual Analogue Scale (VAS), P.S. Kerr's Calcaneal Fracture Score (CFSS). The average age was 41.4 and average follow up period was 74 (12 to 240) months. Results: For follow up period, average VAS is 3.43 and CFSS is 81.23. The sex, age, smoking, injury mechanism, and preoperative, postoperative, postoperative 1 year Bohler angle had no correlation with the prognosis. But the Essex-Lopresti classification of calcaneus fracture, tongue type had better prognosis than joint depression type (VAS : p=0.041, CFSS : p=0.021). Conclusion: In unilateral calcaneus fracture, the sex, age, smoking, injury mechanism, preoperative Bohler angle, postoperative Bohler angle, postoperative 1 year Bohler angle had no correlation with the prognosis of fracture, but in Essex-Lopresti classification, the tongue type fracture had better prognosis than the joint depression type.

• Korean Journal of Applied Biomechanics
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• v.27 no.1
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• pp.45-52
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• 2017

Objective: The aim of this study was to investigate the periodicity of the lower extremity joint flexion/extension angle to compare the local stability between young and elderly women during walking on a treadmill. Method: Eighteen young women (mean $age=21.2{\pm}1.6y$; mean $mass=57.1{\pm}6.1kg$; mean $height=1.61{\pm}0.04m$) and 18 elderly women (mean $age=66.4{\pm}1.2y$; mean $mass=55.4{\pm}8.3kg$; mean $height=1.56{\pm}0.04m$) participated in this study. Approximate entropy (ApEn) was used to determine the periodicity in the lower limb joint angles. Results: The ApEn values of the two groups were statistically greater in the surrogate data test than in the original time series data (p<.05). The periodicity of the hip and ankle flexion/extension angles decreased in the elderly women group compared with the young women group (p<.05). The periodicity of the lower extremity joint flexion/extension angle showed that the ankle joint increased dominatingly in both groups (p<.05); the hip joint decreased compared with the knee joint in the young women group; and the knee joint decreased compared with the hip joint in the elderly women group (p<.05). Conclusion: These results suggest that the lower extremity joint flexion/extension angles of the young and elderly women during walking contained random noises as well as biological signals. In addition, the differences in the periodicity in the lower extremity joint between the young and elderly women may provide some insight in predicting potential falls and be used as a characteristic indicator for determining local stability in elderly women during walking.

• Journal of Welding and Joining
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• v.15 no.2
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• pp.64-71
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• 1997

In order to define the effects on shapes of welding joint, during Post Welding Heat Treatment (PWHT), we have carried out numerical analysis on the several test pieces by using computer program which was based on thermal-elasto-plastic-creep theories for the study. And then, welding residual stresses after PWHT were measured same test-pieces to compare with the results of numerical analysis. The main results obtained from this study is as follows: 1) The distribution modes of welding residual stresses are same on the all test pieces after and during PWHT by the both sides (measurement and numerical analysis). 2) The mechanical difference for change the thickness of plate and bevel angle are not appeared. 3) In a mechanical point of view (like material quality test, welding deformation etc.), manimum bevel angle (40$^{\circ}$.) is more suitable than maximum bevel angle (70$^{\circ}$).

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.499-502
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• 2003

The purpose of this study is to understand the sliding characteristics of the infilling-joint surface using the new devised shear test apparatus with changeable slope for the original infilling materials and the infilling materials experienced cyclic freezing-thawing processes. Three types of the mother rock classified as the igneous rock, the metamorphic rock and the sedimentary rock and the infilling materials were collected for laboratory test. The cohesion according to the slope change of the rock joint shows large variation within ${\pm}$5 degrees but the internal friction angle shows appears the linear decreasing tendency. It is confirmed that the affecting factor of slope change of rock joint at the behavior of rock mass is larger than that of the infilling thickness. Test results show that the cohesion and the internal friction angle in 100 times of cyclic freezing-thawing processes are decreased about 50 percent compared with original one. A further study using various infillings materials would lead to a better understanding of the failure mechanism of rock mass by slope change of rock joint.

• Steel and Composite Structures
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• v.39 no.3
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• pp.337-352
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• 2021

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.3
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• pp.690-696
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• 2013

This study, which is conducted on two groups of skilled people and unskilled people, is purposed to analyze joint angle of lower extremity during short track speed skating in order to find out efficient body position and propose ideal training method. Short Track Speed Skating has a wide range of research areas, but their findings indicate a promising area for further research. Targeting 8 people who are skilled in short track speed skating and 8 people who are not skilled in it, this study analyzes three dimensional images using super-high speed camera to compare differences between these two groups of people. In this study, 6 sections of body positions including right foot push-off, right foot recovery, right foot basic position, left foot push-off, left foot recovery, and left foot basic position were analyzed using 8 super-high speed cameras of VICON. These body positions were analyzed in order to find out joint angles of the hip joint, the knee joint, and the ankle joint. In the section 4 of the inner and outer parts of the left hip angles showed significant difference, and most of the sections of knee joint angles also showed significant difference. In the section 1 and 2 of the plantar flexion, dorsiflexion of ankle joints showed significant difference(p<.001) It was found out that there were differences between groups of skilled people and unskilled people in terms of lower extremity's joint angles such as angles of the hip joint, the knee joint, and the ankle joint.